Note: This is a seattlepi.com reader blog. It is not written or edited by the P-I. The authors are solely responsible for content. E-mail us at newmedia@seattlepi.com if you consider a post inappropriate..

A Historic Year For The Seattle Mariners Bullpen

The Mariners pitching staff has been phenomenal this season, with a Major League leading 2.95 ERA that is greatly suppressed by Felix Hernandez’s 180.1 innings and 1.95 ERA. To put this staff’s performance in perspective, the AL average ERA is 3.86, or almost a full run per game higher than the Mariners. This has allowed the Mariners, who rank 14th out of 15 teams in the AL in runs scored, to, never the less, post the second best run differential in the league.

Historically Good

The last MLB team to finish the season with a sub 3.0 ERA was the 1989 Los Angeles Dodgers at 2.95 and the last AL team to finish with a sub 3.0 ERA in a full season was the 1974 Oakland A’s, also at 2.95 (the 1981 New York Yankees finished with a 2.9 ERA in a strike shortened season). Orel Hershiser led that Dodgers club with 256.2 innings and a 2.31 ERA, while the A’s ace in ’74 was Catfish Hunter with an insane by today’s standards 318.1 innings and 2.49 ERA. (The A’s actually had three starters – Catfish Hunter, Vida Blue, and Ken Holtzman – log over 255 innings).

Both the ’74 A’s and the ’89 Dodgers would go on to win the World Series.

So, in the rarefied air that the Mariners pitching staff finds itself this season, I wanted to take a look at an often overlooked component of any team’s staff – the bullpen.

The Bullpen

While Fernando Rodney has garnered national attention, oftentimes more for his arrow routine than his pitching, Danny Farquhar, Yoervis Medina, Charlie Furbush, Tom Wilhelmsen, and Joe Beimel probably aren’t household names, even in the Puget Sound area. Although Beimel should be known as the now seemingly mandatory relief pitcher on every staff with a wild beard capable of housing small animals.

Including Rodney, this collection of pitchers in the Mariners’ bullpen (we should also include Brandon Mauer who started off as a starter, was demoted, and then recalled to work in the pen) is on a record pace with a 2.33 ERA. Now, of course, a few bad innings over the last 40 or so games of the season could alter that, but the 274 innings logged by the bullpen has been essential to the Mariners’ success.

How Good are They, Really?

Every single member of the Mariners bullpen, except for Furbush, has an ERA under 3, with Beimel sporting the pen’s best 1.27 ERA. But, ERA is a measure of past performance. What should we expect going forward as the Mariners make their last fourth of the season push for the playoffs?

First, let’s be clear that every single member of the Mariners bullpen, again except for Furbush, is out performing his peripheral numbers, some slightly, others by wide margins. Second, there’s nothing to suggest that they can’t continue to do so for the remainder of the season. That said, let’s take a look at two advanced metrics that attempt to predict future pitching performance.

FIP and xFIP

(Definitions from FanGraphs)

Fielding Independent Pitching (FIP) measures what a player’s ERA should have looked like over a given time period, assuming that performance on balls in play and timing were league average. FIP does a better job of predicting the future than measuring the present, as there can be a lot of fluctuation in small samples. It is less effective in describing a pitcher’s single game performance and is more appropriate in a season’s worth of innings.

Expected Fielding Independent Pitching (xFIP) is a regressed version of FIP. It’s calculated in the same way as FIP, except it replaces a pitcher’s home run total with an estimate of how many home runs they should have allowed. Home run rates are generally unstable over time and fluctuate around league-average, so by estimating a pitcher’s home run total, xFIP attempts to isolate a player’s ability level.

Comparing the Mariners Bullpen ERA to FIP and xFIP

Of all the pitchers in the Mariners pen, Joe Beimel has by far exceeded his FIP and xFIP. While his ERA is 1.27, his FIP is 3.47 and his xFIP is 4.16. What this tends to suggest is that Beimel has not only been incredibly lucky with balls in play, but also with fly balls specifically, as can be seen from his home run to fly ball ratio (HR/FB) of 3.3%. League average HR/FB is closer to 3 times that at between 9% and 10%.

With only 35.1 innings pitched, Beimel could easily regress back to the mean this season, or he could continue on this pace. The takeaway is that Beimel is closer to an average pitcher than an excellent one and that the Mariners are reaping the benefits of both good defense and luck when it comes to their set up man.

The same can be said of the performances of Yoervis Medina and Tom Wilhelmsen. Medina’s ERA is 2.18, but his FIP is 3.42 and his xFIP is 3.67 in 41.1 innings pitched. Wilhelmsen’s ERA is 2.29, while his FIP is 3.82 and his xFIP 3.69 in 63 innings pitched.

Like Beimel, Medina is getting lucky this season on both balls in play and with fly balls staying in the park. His HR/FB rate is 6.9%. Unlike Beimel, Medina’s FIP and xFIP suggest that while he is having an excellent season, he is also an above average pitcher.

Wilhelmsen’s numbers are kind of odd in that his xFIP is higher than his FIP, suggesting that he’s been lucky on balls in play, but slightly unlucky on fly balls. His 11.1% HR/FB bears this out. Of course, 63 innings is an incredibly small sample size, so that ratio could easily improve. Wilhelmsen also seems to be an above average pitcher having an excellent year.

Fernando Rodney has also outperformed his peripheral numbers, if only slightly, with a 2.31 ERA, 2.4 FIP, and 2.93 xFIP. He’s had an excellent season by any measurement.

And, not to sound too much like a broken record (round vinyl things that played music back in the 20th century), but Danny Farquhar has also pitched slightly better than should be expected, with a 2.66 ERA, and 2.51 FIP but 3.07 xFIP. A 4.7% HR/FB explains the discrepancy in FIP and xFIP. In this case, a great pitcher having an excellent season.

The only member of the Mariners bullpen who is underperforming is Charlie Furbush. He’s been unlucky all around, but not by that much. His 3.71 ERA is behind a 3.27 FIP and his 3.15 xFIP. He’s probably a half a run better pitcher than he’s shown this season. But, with any of these metrics, he’s an above average pitcher, with some room for improvement with a few bounces of the ball in play.

Take Away

The Mariners pitching staff is having an historic season, with major contributions from their bullpen. To the extent that the majority of the pitchers in the pen are having career years, this year may be one of those rare “aligning of the stars” seasons that must be taken advantage of because in all likelihood next year should see some regression.

Note: This is a seattlepi.com reader blog. It is not written or edited by the P-I. The authors are solely responsible for content. E-mail us at newmedia@seattlepi.com if you consider a post inappropriate..